Alveolar TiO2-β-SiC photocatalytic composite foams with tunable properties for water treatment

Abstract

New alveolar TiO2-β-SiC photocatalytic composite foams gathering within a ready-to-use media, the TiO2 active phase and the β-SiC alveolar foam structure have been prepared through a Shape Memory Synthesis (SMS) replica method. They have been obtained by incorporating TiO2 powders inside the infiltration slurry used for transforming the pre-shaped polyurethane foam into its corresponding carbide. The photocatalytic composite foams contained 16 wt. % and 24 wt. % of TiO2, most of them being available for the reaction by being located in the external layer of the foam rather than dispersed within the foam matrix, so that no further post-synthesis immobilization process was needed for coating the foam with TiO2 active phase. The adsorption behaviour of the TiO2-β-SiC composite foams towards the Diuron pollutant in water was tuned by applying a final calcination treatment to the as-synthesized foams within the 400–700 °C range, that allowed to tune the amount of residual unreacted carbon within the foams, while allowing the formation of small TiO2 crystallites via the selective oxidation of TiC carbide, and thanks to the β-SiC resistance to oxidation. The TiO2-β-SiC composite foams calcined at 700 °C outperformed a reference β-SiC supported foam TiO2 catalyst in terms of diuron degradation, while the reference foam remained more efficient in terms of mineralization rate.